Leather burnishing and plating



Feb. 25, 1947. B. s. CROSS 2,416,289

. LEATHER BURNISHING AND PLATING Filed Feb. 5,- 1942 zPatented-Feb. 25,

orrics LEATHER BURNISHING AND PLATING a Bert s. Cross, st. Paul, Minn.,assignmtoy Minnesota Mining & Manufacturing Company, St.

Paul, Minn., a corporatlonof Delaware Application February s. mia-serialNn. 429,695

` 1 claim. (c1. 69-1) This invention relates to leather working and moreparticularly to improvements in apparatus for leather burnishing,polishing, glazing, plat'- ing and the like. Improved equipment novel totheleather working art may be employed .in the leather finishing stepsmentioned by reason of a heat-resistant, oil resistant cellulosicsheeting employed as an element of such equipment permitting theemployment of high-speed apparatus.

In the art oi.' iinishing leather, the leather is brought to its. iinalfinish by one or more of a number of steps, such as bufling, glazing,burnishing and plating. and the leathermay be plated or pressed beforeor afterthe buiiing and plating steps. Various methods have beenemployed for working .the leather to finish and polish it and to improveits texture and where desired, to bring its fat and other oilyconstituents to the surface, such Y as by burnishing with steel, brassor glass rolls,

or by plating it in a hydraulic press with a sheet of ordinary lpaperbetween the leather sheet and a face of the press jaw. However, certaindimculties arise from the use of these materials, some of which maybe-enumerated as spotting of the glazed leather by deposits thereon inlump form of the worked out residue .or oils, andV scratching of theburnishing surface, which consequently decreases itsl utility andprovidesuneven surfaces which further tend to effect deposits of residueand oils. Particularly do these factors slow `up production, tending toincrease its cost anddepreciate the qu'ality of the finished leather.Further, in plating leather, e. 8., in a hydraulic press.

- buck shot" to be found in the hides ofica'ttle and the resultingrleather sheets. In the case of burnishing with steel, brass or glassrolls, as aforesaid, the surface of the roll is'gouged or roughened,with the result that vthis roughness thenA scuffs the hides. When thishappens, the roll requires replacement, which is expensive andcumbersome.

On the other'hand, after lencountering buck sho of the like duringuse,my burnishing sheet has ymuch less'tendency `toigouge or scufrthework, e. g.. a leather sheet; rfurthermore the bur- 2` nishing surfacecan be replaced cheaply and quickllh A salient aspect of the presentinvention involves improvements in the art of burnishing leather, whereleather to be polished isA brought .into contact with a rotatingcylinder covered with my composite burnishing sheet,` or into contactwith a rapidly moving belt of my sheet material. It is one of theobjects of this invention to produce 'improved apparatus for` burnishingor finishing leather. For example, in its broader aspects, the apparatusmay comprise a power-driv. en burnishing drum and an adjacent rotatablymounted roll between which the leather piece to be finished may bepassed. theroll being readily movable toward or away from the drum forforcing the leather piece against the surface of the drum. The surfaceof the drum' vis covered with a leather working sheet of the typedescribed, which may be spirally wrapped about the drum and its looseends secured by suitable fastening ing roll and spaced pulleymembers,the improved devices or which may be wrapped straight around the drumwith its ends extending into a longitudinal slotvin the drum, equippedwith take-up leather work material passing around the burnishing rolland pulley members in the form of a belt. In this embodiment, a pressureroller is mounted adjacent the bumishing roll or pad for forcing theleather piece against the face of the leather working belt. Theinvention also includes improvementsin plating apparatus in that byreason of the oil-resistant nature of my improved plating element,pitting or corroding of the platen of the press is substantiallyeliminated in -additio'n to the fact that my plating element has a muchlonger life than such elements customarily employed by the art.

The burnishing and plating sheetv of this inven.. tion is provided witha burnishing surface formed of a. coating which may advantageouslycomprise a heat-.convertible synthetic resin, e. g., a phenolaldehyderesinadhered to a paper or other sheet. The paper or cloth backing is'impregnated to some extent with the coatingv material, but the coatingmaterial preferably does not extend through the sheet. The thickness ofthe surface coating may vary somewhat from .0005 to .004 yinch more orless. I t is of considerable impor'- tance that the coating material beheat-resistant and it shouldlhave a softening pointhigher than thetemperatures attained the finishing treatment in order that the coatingmaterial will l not adhere or oifset onto the leather piece.Satisfactory results have been obtained with coating materials which donot soften below 150 C. Furthermore, the coating material should not beaffected, such as softened, by the oils of the leather with which itcomes in contact. It is also of considerable importance that theburnishing and plating surface be smooth and free of -nibs andrelatively small particles, such as may be formed from dust in the airor dirt in the resin. Care must be taken in the preparation ofthe resinto avoid formation of jelly-like particles which may conglomerate toform hard particles that may mar the'leatherv surface to be finished.Though presently considered less advantageous by reason of lack of highheat-resistance, the burnishing and plating coating may consist of thehardened product of a film-forming inorganic material, e. g., a sodiumsilicate solution, with or without modifying or insolubilizing agents,such as precipitated chalk (CaCOs) sodiumuosilicate, zinc oxide, etc.Generally, sheets of the type described When employed in platingleather, do not require a surface as glossy-smoothas in burnishing.

- It is believed the invention will be readily understood from thefollowing description in conjunction with theV accompanying drawing, inwhich:

Figure 1 is a side elevational view of one embodiment of my improvedleather burnishing apparatus:

Figure 2, a top-plan view of the apparatus as shown in Figure l;

Figure 3, aside elevation of another embodiment of my invention;

Figure 4, a top-plan view of one embodiment of my leather-finishingsheet, with the two upper coatings thereof partially removed, toillustrate the construction of the same; y

Figure 5, a vertical sectional view of the composite sheet oi Figure 4;

Figure 6, a verticalsectional View showing a modification of theleatherworking sheet material of Figs. 4 and 5 to include a further supportinglayer or sheet; and

Figure 7, a vertical sectional view of my improved plating apparatus. i

Referring to Figs. land 2of the drawing, the reference character Iindicates a drum mounted on a shaft II and connected to a suitablesource of power by the belt I2. The drum I0 is preferably formed ofyleldable material, as rubber or the like, or if a metal drum isemployed it may be provided witha covering of rubber or felt or thelike. Secured about the periphery of the drum isv aleather working sheetI3, comprising abase of paper or cloth I4 to which coatings kI5 and I6,as

shown in Figs. 4, 5 and 6 hereinafter described,-

are applied. A rotatably mounted presser roll I'I,

-preferably formed with a hard rubber surface, is

disposed adjacent the drum I0 and it is to be understood that the drumI0 and the presser roll I'I are suitably mounted in frame members notshown. As shown in Fig. 1 the leather Work sheet I8 is adapted to bepassed between the presser roll I1 and the drum I0 to receive tli'enishing treatment and accordingly the presser roll Il may members" whichmay comprise adjusting screws I9 carried in slots 29 in the brackets 20.

As shown in Fig. 2, the working sheet I3 may be spirally wrapped aboutthe drum I0 with its ends secured to the drum by suitable mechanicalfastening members, such4 as rubber faced metal clamps, or by a suitableadhesive. such Ias resins or the like, which are not decomposed 'byheat. It is alsoto be understood that the ydrum I0 may be provided witha longitudinal slot in which are housed take-up members which maycomprise a pair of rollers equipped with a dog and ratchet, and in thisform the leather working sheet I3 vmay be wrapped aroundthe periphery ofthe drum I0 with the sides of the leather working' sheet I3substantially parallel to the edge of the drum. The ends of the workingsheet are fed into the take-up reels which are tightened to retain theworking sheet tautly about the periphery of the drum.

The drum may be driven -at a speed of from approximately 4000 to 6000feet per minute and the leather may be fed. between the drum and roll atabout 30 feet per minute. Thus the burnishingoperation maybe performedrapidly with Y .my improved apparatus.

In the embodiment of Fig. 3 the leather working material is employed inthe form of a belt 2I which passes around a bumishing roll 22 andpulleys '23 and 24, the pulley 23 being driven by theemotor 25 to effectmovement of the leather be moved toward or away from the leather sheetI8 and the drum IIJ to force theleather piece I3 against theworkingsheet I3 on the surface of the drum I0. To control its position,the shaft of the presser rou n is provided with adistame working belt2I. A presser orzbilly roller 26 is rotatably mounted in suitable framemembers.

as are the roller 22 and the -pulleys 23 and r24,A

and is adapted to be moved Itoward and away from burnishing roll 22 toforce the leather piece I8 adapted to be passed .between the rollers 22and 26, against the leather working belt 2i. The

billy roller 26 isprovided with Asuitable adjusting means which maycomprise brackets 20 having slots 29 inn which the ends of the rollershaft may be journalled, and an adjusting screw I9. The rollers 22 and26 may-be provided with somel what yielding coverings similar to thoseon the drum I0 and roll Il of the embodiment of Fig. 2. Referring toFig. 7 of the drawing wherein is shown my'improved leather platingapparatus, the reference characters 3| and 32 indicate the.

' ment having either a resilient or solid facing element 35 upon whichthe leather strip I8 is smoothed and compressed, or punched by thereciprocatingv weighted platen 3|. The facing element 35 is surfacedwith a. leather working sheet. 36 which is readily removable, may beretained thereon by adhesives or adhesive tape and which may comprise abase of paper or fabric I4 having a smooth oiland heat-resistant coatingI6; and if desired an lmpregnating or filler coating I6, as shown inFigs. after described.

The leather working material, which may be f formed in sheets or stripsI3 or in belt'form 2| or the like, is shown in detail in Figs. 4 and 5and comprises, for example, a'paper or fabric b'ase I4, saturated with afiller I5 and surfaced 4. 5 and 6, herein- Y ananas l with a compactheatand oil-resistant smooth surface I6, all of which are hereinafterdescribed in greater detail. The modiilcation shown in Figure 6discloses a leather working material, as illustrated in Figs.

4 and 5, having laminated to the base material 4iicient life to meet therequirement of modern leatherfworking industries and will at'the sametime produce results of superior quality to those obtained with presentglass and metal working faces, provided certain basic principles befollowed. Irwill now give illustrations by which such -materials can bemade, it being understood that the illustrations are examples only andare not intended' to be limitative.

The leather working sheet material comprises a tough flexible backingsheet I4 such as cloth,

. paper, vulcanized fibre, and the like, or `combinations of the same,having the fibres covered, or one face of the backing sheet covered, by*a smooth, 'compact heatand oil-resistant surfacing I5 and I6. (Thei'lller coat I5 is normally advantageous but not essential.) Thesurfacing must be suilciently flexible to serve as a wrapping I3 aboutairum I0, e. of 10 inches or more in diameter, or used as a belt 2|without` cracking, while being mechanically flexed. Such lsurfacingshould also be hard enough lto present a lrm surface to the work and besufficiently un.-l aiected by the heat encountered during use so as notto become soft and/or sticky. Likewise the coating must .be one thatdoes not become brittle and break up when subjected to heat duringthetlnlshing operation. In order to produce the compact Isurfacedesired, which is free 'of protuberances and particles and issubstantially smooth, it is necessary to achieve -two conditions, viz:(1) there must be enough of the surfacing medium present, in addition tosuch amounts as may be absorbed by the backing, to

form a continuous, but not a thick film, and (2) tional coatingapparatus which spreads and smooths a -relatively thin illm over thesurface of the backing illling its voids. This coating is then set up byrunning the material into an oven and allowing it to dry (e. g.. atabout 80 C.) until danger of adhesion is past, whereupon the coatedmaterialis rolled linto loose coil form, and the resinous material isfurther set up for a period of approximately 16 hours, more or less, atsubthe coating material, as' applied, may advanta- 'Y Y geously beliquid enough yto ilow out" after being spread on the backing, thusproducing directly the relatively smooth, compact surface desired..

Where certain protuberances for roughness exists after the coatingoperation, one eilective way to correct this condition is to pass thecoatedsheet between heated, smooth-surfaced calender rolls.

Example 1 The' backing I@ is preferably a rope'rcylinder paper (e. g.,of a weight of the order of 130 lbs.4

per ream oi 24" x 36" sheets) having a thin, ilexible, glassy-smoothsurfacing in the nature of 'heat-resistant and heat-hardenable resinousmaterial prepared and coated, for example, as foilows: a solution in theapproximate proportionate parts of 80% resin solids, such'as Bakelite (aphenol-formaldehyde resin made from approximately 94 parts phenol and 80parts of 371/2 formaldehyde), to 20% solvent, preferably ethylene'glycol monoethylether (or other solvents such as alcohols, ketones ormixtures thereof, and the like, which are good solvents for theresin andneither vaporize so rapidly as to ,prevent the resin to flow outproperly during coating, nor so slowly as needlessly to delay thecoating process) is coated on the paper by use of a convenstantially C.'This period oi heating is conrtrolled'in proportion to the ydegree ofheat used for curing, as for example boosting the curing ltemperature to160 C'. will reduce the curingtime substantially, e. g., to a period offroml to 4 hours, dependent upon the nature of the resin applying twocoatings oi phenol-aldehyde resins, with lat least partial curing of thefirst coat be fore application of the second coat.

The rst coat may be 12 grains of phenol-alde.

hyde solution of 50 percent concentration per 4 x 6f area oi.' paper orbacking sheet, and the second coat may be 5v grains of 50 percentphenolaldehydesolution for the same area.

Example 2 When a less viscous coating is vapplied to back# ing sheets ofsuchporosity, its] absorption into the backing often necessitates thefurther application of' additional coatings until the desired smoothsurface is procured, as for example a coating of 50% resin solids maybe'applied and set up for 1/2 hour at 100 C.,f,ollowed by an additionalcoating oi 60% resin solids set up for one hour at 1 100 C. to preventrunning, and cured in coils for` 16 hours, more or less (sometimes up to48 hours), at 100 C. I. f

It has been found that economical coatings may be applied in varyingsolid percentages from 90 to 50%, dependent upon the porosity of thebacking material which controls the smoothness of the illm in proportionto the viscosity'of the coating. material and the number of coatingsapplied. In the event that some slight running or roughness of surfaceis present, the coatings may be 'smoothed down by passing the coatedsheets through heated smooth-surfaced calender rolls; also the coatingsmay be smoothed by suitable sanding and polishing, after the materialhas been properly set up and, where desired, an additional very thincoating of less viscous material may be applied.

y Example 3 Further examples of suitable coatings which `may -be usedfor leather Working requiring less heat. resistance and waterproofnessthan that of pressing or burnishing are those secured by application ofcommercially prepared sodium silicate solutions. For example, whencoating'a lb. rope cylinder paper with a single surfacing, a fluidcomposition of 38.4% solids consisting of 9.1% sodium oxide and,29.3`%silicon dioxide to 61.6% solvent, as water, will illl the pores andproperly coat the backing, the solids content, however, may vary Iinproportion to the porosity of the backing material used, and the numberof coatings to be applied, for example solutions comprising from 6.4% to36.9% sodium comprising approximately `7 L oxidev toI from 24.7% to23.8% silicon dioxide. Likewise, mixtures of varying percentages to thesolvent give solutions of a desired viscosity and produce relativelythin, glassy-like coatings on the particular backing to which thematerial is aplied. This coating material is preferably dried at normalroom temperature or mild heat, with the backing placed in a horizontalposition,A

whereupon, -after suilicient curing, the coated material is ready foruse. This sodium silicate i coating may be rendered more heat-resistantby treating the solution with modifiers, such as tion bodied up to aviscous solution and nally set up after` lamination of the coated andreinforcing sheetings.

Where the reinforcing member 28 is employed it is preferably presizedfor further securing its adherence to the coated sheeting and forstrengthening the tear-resistance of the strucprecipitated chalk(CaCOa), calcium silicate, sof i diumY uosilicate, zinc oxide, etc.

I have further found that the porous sheeting may be sized and its voidslled with a material as disclosed in Example 3, and a resin coating inthe nature of phenol-aldehyde applied, as described, forms a smoothcompact surfacing which is both heat-resistant and waterproof. Further"the void-fiilling materials may vary in composition from the surfacingfilm and consist of such materials as casein, glue, varnishes, shellac,or mixtures of the same, .as for example glue and resin in the nature ofphenol-aldehyde and the like, all of which are provided with a surfacingofthe herein described characteristics.

The preceding examples illustrate several lmethods and materials formaking my improved leather working product which, yto improve thenishing of leather, lmust possess the characteristics of smoothness and.resistance to oils and heat to give theleather surface a smooth grainedappearance without spotting or leaving deleterious impressions.

Accordingly, a toughvpaper material as illustrated possessing uniformstrength along and across the sheet is preferred.

However, suitable cloth material asy Drill" or Jeans, and the like, maybe substituted so Vthat when coated with a heatand oil-resistantsurfacing as resin in the nature of phenol-formaldehyde,urea-formaldehyde, furfural-phenoL glyptol, and the like. which may alsobe employed with paper sheeting, there is provided a tough semi-ilexibleresilient sheeting capable of withstanding the rigid requirements ofleather Working. Vinyl resin coatings may also be employed where hightemperatures are not encountered in use. 4

Any of the surfacing materials hereinabove mentioned may or may not becolored or shaded with 'suitable 'dyes or pigments as lamp-black,

" burnt umber, zinc oxide, titanium oxide, chrome oxide, barium chromateand the like, for marking or decorative eifects as desired.

To provide a stronger sheeting, the vreinforcing member 29 as shown inFigure 6 is a cloth mate` rial and the adhesive 27 is preferably heat orsolvent activated in character and comprised of resinous or gluematerial. The adhesive 21, when formed of animal glue, may be acomposition prepared by warming and mixing, and may be coated onto'thereinforcing sheet material, with subsequent adherence of the coatedsheeting to the y i glue coated side of the reinforcing material. Thelaminated structure is thereafter loosely Vrolled and stored underconditions to properly set up the glue. The type of glue or protein, orthel like,

ture. In the glue lamination illustrated, a 29% glue sizing solution is-used with or without an insolubilizing treatment for the adhesive orsiz- I adhesive. a size in the nature of a phenol-formaldehyde resin,thinned with 35 percent of such thinner as ethyleneglycol,monoethylether, alcohol, or the like, is coated over the reinforcingmember 28 and set up by .evaporationof the solvent.

In burnishing or polishing natural or artiiicial leather, and sheetmaterials of generally'comparable character, the surface temperaturesproduced by friction may vary within a substantial range, depending upon the machine speed and other conditions of polishing. Likewise thejaws or platens of the plating apparatus may be heated. Where thepolishing'surface, i. e., the surface coating, of the burnishing andplating sheet consists of a heat-convertible synthetic resin, such as aphenol-aldehyde resin, it may be used under a wide range of conditionsand will withstand any temperature likely to be encountered in practice.'Ihe quality of the leather plated in accordance with my invention isimproved in that oils in the f .leather are not absorbed by my leatherworking REFERENCES CITED The following references arev of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 2,109,687 Buckley Mar 1, 19382,186,679 Lade Jan. 9, 1940 2,005,885 Brindley June 25, 1935 1,542,447Harding June 16, 1925 2,033,894 crockford Mar. 1o, 1936 2,071,563Newcomb Feb. 23, 1937 2,059,583 Jackson i Nov. 3, 1936 1,687,968Bredenberg Oct. 16, 1928 1,858,192 Shaw ..-'May 10, 1942 2,098,082 BowenNov. 2, 1937 2,021,172 Bucy. Nov. 19, 1935 82,883 Shepherd Oct. 6,'18681,090,664 Wait Mar. 17, 1914 '1,071,519 Hanish 'Aug. 26, 1913 Y FOREIGNPATENTS Number Country Date 349,761 Italian June22, 1937

